The DJI Inspire 1 is an incredible drone. In my tests and comparison of the X3, X5 and X5R cameras on the DJI Inspire 1 Pro I found that especially the Zenmuse X5R RAW camera delivers amazing images in 4K. But what about X5 ND filtration? On sunny days just closing the iris is not enough. So which is the best ND Filter for the DJI Zenmuse X5 and Zenmuse X5R cameras used on the DJI Inspire drone and DJI Osmo handheld gimbal? The Best DJI X5 ND Filter I found 5 6 different ND filters I could test both with the DJI Inspire 1 RAW and with the DJI Osmo RAW and compared them to each other that is both compatible withe the Zenmuse X5 and the Zenmuse X5R camera. First I compared the filters in the field under varying light conditions, then I did another comparison in our test lab. Check out the video to see the results. Here’s an overview of the different filters I tested and their properties explained. In the conclusion I will summarize my findings and recommendations. Polraoid VariND Weight: 15g ND filtration: 1-8 stops Weight balancing: filter, extension ring and 49mm fotasy lens hood (EU: Link) The Polaroid VariND is the most affordable of all the filters. It performed well, just had a slight orange tint. There are no hard stops, so it is not as convenient to use as the B+W. In order to be ok with gimbal weight you should use an extension ring and 49mm lens hood. The original DJI lens hood can not be used when this filter is on. The filter has no IR cut. US: BUY HERE EU: BUY HERE B+W XS-Pro MRC VariND Weight: 26g ND filtration: 1-5 stops Weight balancing: filter and 49mm fotasy lens hood (EU: Link) The B+W XS-Pro MRC VariND is a lot more expensive than the Polaroid, but build quality is excellent, it has hard stops and it looks quite neutral with a slight orange shift similar to the Polaroid. In order to be ok with gimbal weight you should use 49mm lens hood. The original DJI lens hood can not be used when this filter is on. The filter has no IR cut. US: BUY HERE EU: BUY HERE Heliopan VariND Weight: 49g ND filtration: 1-6 stops Weight balancing: Too heavy. Filter is not recommeneded. The Heliopan VariND feels like a solid product. It has hard stops and accurate markings and the image looks very neutral. Only at the far end I noticed an ND cross, so the ND filtration was not even. Unfortunately this filter is too heavy as an X5 ND or X5R ND. The filter has no IR cut. BUY HERE Tiffen XLE Series Intermediate 3.0 IRND Weight: 13g ND filtration: 10 stops Weight balancing: filter, DJI weight ring, and 46mm fotasy lens hood The Tiffen XLE Intermediate IRND filters 10 stops of light and has an IR cut built in. This was too much even for a sunny day and the IR cut turned my image green to counter magenta shift. The result was not neutral, so this option is not for me. BUY HERE Tiffen XLE Series Premiere IRND 3.0 Hot Mirror Weight: 13g ND filtration: 10 stops Also available in: Weight balancing: filter, DJI weight ring, and 46mm fotasy lens hood Just like the intermediate, this Tiffen XLE Hot Mirror IRND filters 10 stops of light. Too much exposure reduction for my tastes and the IR cut turned my image green. I was not happy with the result. If you need a good IR cut filter this Hot Mirror seems better suited than the intermediate option though. BUY HERE Formatt Hitech Firecrest IRND 1.5 Weight: 8g ND filtration: 5 stops Also available in: 1 stop, 2 stops, 3 stops, 4 stops, 6 stops, 7 stops, 8 stops, 9 stops, 10 stops Weight balancing: filter, DJI weight ring, and 46mm fotasy lens hood Just like the two Tiffen filters, this Formatt Hitech Firecrest filter has no variable ND functionality. It filters 5 stops of light and according to the manufacturer there is also an Infrared filtration built in. The image was very neutral and had a slight blue shift that I liked. It is the lightest of all the filters tested and not too expensive. US: BUY HERE EU: BUY HERE Conclusion For me the Formatt Hitech Firecrest IRND 1.5 was the ideal filter for sunny shoots. The neutral image looks clean, it is light and affordable and even has some IR reduction, though I did not seem to need that when testing the other filters. As a VariND the B+W seemed like the best option. Especially for the DJI Osmo as an X5 ND it would be ideal with hard stops and a clean image. As a budget option the Polraoid would also do the job, but another adapter ring is needed to balance it properly. I hope this review was helpful for you. If it was please consider buying your gear through our recommended retailer’s links. And if you worked with any of the filters or other X5 ND filters please let me know about your experience in the comments.Read more
While capturing and crafting moving images may be our primary focus, there’s a lot to be gained by taking your photography just as seriously. I’d like to quickly highlight six reasons why you should spend as much time capturing stills as you do motion. Actually… I’ll take it one step further. As much as I love even shooting with my iPhone, and much of what I’m about to say applies no matter what medium or camera you use… preferably you should put away your digital cameras altogether and get yourself an all-manual SLR. Shoot film, and everything I’m about to say will double or triple in value. It’s not simply about composition and framing. It’s about light itself and developing a tuned and calibrated internal compass for exposure, color and light… Let’s start with a famous quote that I often remind myself of. – “Your first 10,000 photographs are your worst.” – Henri Cartier-Bresson We seem to forget this all too easily, or not acknowledge at all that it applies to cinematography also. If you really want to become a cinematographer who is recognised and known for producing works of compelling, emotive visual art, then you need to start thinking and operating on a totally different level to what you may be used to. You need to get your head out of video and surround yourself with art. I have found that seeking out other related visual input, such as architecture, design and photography has led to a greater discovery of my own interests, preferences, style and creative voice. 1. Inspiration I find far more inspiration following some photographers’ Instagram feeds than I do in most Hollywood movies. It’s amazing what a single still frame is capable of communicating. If you’re not an Instagram junkie yet, get on board even if you have no intention of sharing your own work. Follow photographers that consistently create imagery that inspires you and makes you feel something. It’s fun to share your own work too, and although I started years ago just with iPhone shots using the apps “ProCamera” and the fantastic monochrome iPhone camera app “Lenka”, lately my work has all been 35mm film scans, which kind of takes the “insta” out of it altogether, but whatever… It’s a snapshot of my own journey in imaging and you can use it the same way. Let others discover your work and be inspired, we’ve all got a different story to tell. Pinterest is another fantastic platform for searching out and tracking ideas and inspiration you want to draw from in your own work. The great thing about Pinterest is you can pin other people’s work, and images that others share onto your own organised boards. For instance, I keep separate boards titled “Creative Shot Ideas”, “Lighting and Composition”, “Lighting and Color Mood References” and “Color Grading References”. The great thing about it, is it’s a constantly growing and evolving library curated by you. It is always online and accessible from anywhere on your phone or tablet. You can be on a location recce and swipe through a library of images that immediately gets ideas flowing. 2. Intent The ability to reduce a scene that you intend to shoot in motion down to a single frame, one simple moment, a fraction of a second captured in time will give you a strong and focused purpose for what you are trying to achieve. One of the biggest weaknesses I see with videographers that like to call themselves cinematographers is they have no sense of purpose. They simply don’t know what they want to achieve, they have no intent. Without intent, you are just someone with a camera. You may know how, but you don’t know why. Believe me, knowing why is far more important, and it’s the more difficult question to answer. “How” is simply the question of a technician. “Why” is the question of an artist. A technician can know how to operate a camera and be a perfectly capable videographer, but that is not cinematography. Cinematography is an art form, it is about knowing why, not just how. It’s about intent, and every decision creative or technical is intentional. A love for photography instills purpose and intent. 3. Technical Competence Ever heard of the Sunny Sixteen Rule? Neither had I, really. Or at least I never bothered to entrench the very simple mathematics of exposure into my head until I started shooting film on a vintage Russian SLR with less than trustworthy metering. Sure, I have a Sekonic L358 which is always in my bag but, more importantly, I learned it is possible to calibrate your eyes and brain to be a great (and often accurate enough) light meter. Illustrated is a simple vintage Rolleiflex TLR exposure guide based on 10 deg DIN film speed, which is equivalent to about ISO/ASA 50. The sunny sixteen rule states: “On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight.” This means: f/16 at ISO 100 for 1/100th sec (or 1/125th sec if that’s the closest shutter speed) f/16 at ISO 200 for 1/200th sec (or 1/250th sec… it’s close enough) f/16 at ISO 400 for 1/400th sec (or 1/500th sec) From that point on, it’s easy to calculate in your head. If it’s sunny, and you’d rather be at f/5.6 in terms of desired depth of field, and you’re shooting ISO 200 speed film, then you simply calculate that f/5.6 is +3 full stops from f/16 (count them… f/16, f/11, f/8, f/5.6), so you either need to increase your shutter speed by 3 (1/500th sec will probably be OK) or reduce the exposure by 3 stops by using an ND8 filter. That’s for stills, but the math works the same for video… you’re just calculating for slower shutter speeds. If it’s slightly overcast, the rule still works but at f/11 for the shutter speed at the reciprocal of the film ISO speed. Overcast conditions you’ll base the same calculations on f/8 and if it’s heavily overcast, you’ll base it on f/5.6. Shooting at sunrise or sunset? You’ll base it around f/4. The more you shoot stills in varied conditions and practise your metering, calculating in your head, using a meter, comparing and building on that experience, the more you will know about the technical requirements of a video shoot just from seeing and visiting locations no matter how brief the recce. Learn from shooting stills, practise the math, and you’ll know it all for video too… when and how to add a stop, reduce a stop, whether it is due to adjustments in frame rate, lighting conditions, filtration or shutter angle. 4. Confidence Imagine you walk onto a location or set, look around and know immediately how you’ll light it, or how you’ll work with the natural light. The image you see in your minds eye… it should immediately come to mind, you can see the focus, the DOF, foreground elements, background elements and where and how action will take place. You’ll know how much light you need, or if you have to make technical compromises due to creative limitation and how those compromises should be made. That’s confidence… knowing the how, why, what and where. It takes practise and one of the best and most effective means to practise is honing your all-manual photographic skills. 5. Practice If your first 10,000 photographs are your worst then you’d better get shooting. It’s far easier to take 1000 still photographs, mistakes and all, and learn something from every exposure than it is to set up and shoot 1000 scenes in motion. Photography is a fantastic place for experimentation. It really doesn’t matter whether something works or not as long as you learn something from it. Over-exposed, under-exposed… one stop, maybe two stops, it doesn’t matter if you end up understanding what caused the result. The beautiful thing about shooting film is you’ll soon realise you’ve got a margin of error for exposure that you typically won’t find shooting digital. You can still scan the negative and most of the image is retrievable, your exposure is just sitting on a different part of the response curve, and there may be consequences in contrast and grain. You will start connecting parallels between your film exposures and what is happening digitally with a digital image sensor, and you’ll realise that even though the response of film and results are a bit different, the principles are the same. 6. Diversity We all get stuck in a rut at times, and typically find ourselves shooting within a certain genre or style. Often times this is determined by the type of work we do, be it weddings, corporates, promotional work or commercials. Photography gives you an easy opportunity to snap out of your normal routine. Sure, your best images will probably come from your travels, holidays, or trips to exotic or interesting locations, but that’s easy. It’s much harder to look for and find beauty in day to day normality wherever you are, and make an effort to turn the normal and routine around you into art. Cause and Effect There’s no result without hard work, but if you want to really push yourself, and see your work stand out among the ever increasing crowd of mediocre image makers, one sure way to make it happen is to get serious about photography. Do yourself a favor, get an uncomplicated all-manual SLR and shoot film. You will take a lot of terrible photos, but you’ll also capture some magic. The more you shoot, the better the ratio of good to bad shots will get. You’ll learn tons, and what you learn technically will influence how you shoot digitally. It will strengthen that internal compass, the voice inside you which instills confidence through experience. You’ll discover your voice, your style, your aesthetic, and it will become internal to everything else you do. Best of all, it’s a lot of fun.Read more
Let’s face it, slow motion is bad ass. You don’t get more bad ass than this amazing shot of a .500 S&W Magnum by Herra Kuulapaa (www.kuulapaa.com). While this may be an extreme example, and it’s a still, not a grab from motion, nothing gets the imagination going quite like the ability to shoot high frame rates. Give yourself the edge by understanding the fundamentals of global vs rolling shutter, shutter angles and exposures at high frame rates. A few weeks back I wrote an article “8 Essential Steps to Perfect Exposure – The Knowledge Any Cameraman Should Have”. If you haven’t read it yet, now would be a good time to do that, and then come back to read this one. 1. Mechanical Shutter In a film camera, the shutter is a mechanical rotating mirror. As it rotates 360 degrees per exposure it alternates covering and uncovering the film gate for a particular amount of time. The RPM of the shutter is mechanically fixed and determined by the frame rate, and the exposure time is determined by the shutter angle. During exposure the film is held perfectly still, often with registration pins. While the mirror shutter covers the film gate, the pins mechanically disengage and the pull down claw physically advances the film to the next unexposed frame. 2. Rolling Shutter Many electronic shutters in digital cinema cameras feature a rolling shutter, where data is read out line by line from the top of the sensor to the bottom before being reset ready for the next frame exposure. A rolling shutter can exhibit a noticeable skew of would-be vertical lines in the image if either the camera or subject is moving quickly across the frame. This can create unwanted motion artifacts warping the whole image if the sensor read-out is particularly slow and there is fast motion in the frame. Most rolling shutters are incredibly fast, minimizing potential problems. Red and Arri among many others employ rolling shutters, and the results can lend a more “cinematic” feel than a global shutter. Even extremely high frame rate cameras such as the Phantom digital cinema cameras from Vision Research employ rolling shutter, but with a readout-time of only 1 millisecond. In this chart you can compare rolling shutter readout-times of different camera models we tested in our lab: 3. Global Shutter A global shutter differs from a rolling shutter in that at the end of a full exposure, light is blocked entirely across the sensor all at once while data is then read and it is reset for the next exposure. A global shutter preserves the perfect vertical alignment of vertical lines or objects moving horizontally through the frame. However, the feel of motion can be noticeably different. Depending on how a global shutter is implemented, there can be a small cost in light (fill factor) and possibly dynamic range when compared to a rolling shutter. 4. Shutter Angle Shutter angle is a term that refers to the actual physical angle of the opening in a rotating mechanical shutter in degrees. The angle of the opening determines the duration of the exposure as the shutter rotates. Mechanical shutters for the most part are gone in digital cinema cameras, but often the terminology has stuck. Shutter angle is your control of motion blur. The longer the exposure, the more motion blur, the shorter the exposure, the sharper any moving objects will appear. It can be calculated easily to a fraction of a second exposure time. Exposure time (1/x sec) = Frame Rate x (360 / Shutter Angle) For example, at a frame rate of 24fps at 180 degree shutter (180 degrees is considered normal): 180 degrees: 24 x (360 / 180) = 1/48th second Here is a whole table calculated for 24fps for shutter angles up to 220 degrees: 15 degrees = 1/576 sec 20 degrees = 1/432 sec 40 degrees = 1/216 sec 60 degrees = 1/144 sec 80 degrees = 1/108 sec 100 degrees = 1/86 sec 120 degrees = 1/72 sec 140 degrees = 1/62 sec 160 degrees = 1/54 sec 180 degrees = 1/48 sec 200 degrees = 1/43 sec 220 degrees = 1/39 sec Any change in shutter angle changes the exposure time, and will need to be compensated for with a change in aperture to maintain correct exposure. Of course a change in aperture will affect depth of field. So if depth of field needs to remain unaffected also, the only thing left is to add ND filters (if reducing light to compensate for a longer exposure time) or increase the actual light levels illuminating the scene (if compensating for a shorter exposure time). If we consider 180 degrees as the base (normal) angle as “Full Exposure”, the following compensation table applies. Shutter Angle F-Stop/T-Stop Compensation 197-200 Close 1/4 166-196 Full Exposure 148-165 Open 1/4 135-147 Open 1/3 121-134 Open 1/2 111-120 Open 2/3 99-110 Open 3/4 83-98 Open 1 74-82 Open 1 1/4 68-73 Open 1 1/3 61-67 Open 1 1/2 56-60 Open 1 2/3 50-55 Open 1 3/4 42-49 Open 2 37-41 Open 2 1/4 34-36 Open 2 1/3 31-33 Open 2 1/2 28-30 Open 2 2/3 25-27 Open 2 3/4 22.5-24 Open 3 5. High Frame Rates In the age of digital cinema, more than ever before there is a demand for high frame rates in our cameras. This used to be a specialty requirement but is now expected. Capturing the spray of ocean waves in crisp frozen detail, liquids pouring or simply the beauty of smooth slow motion is no longer out of our reach. Many cinema cameras can now shoot at least 60fps if not much higher. Vision Research has been on top of extreme high speed cinematography for some time. While 1000 – 2000fps is still out of reach for most of us, cameras like the Phantom Flex 4K are pushing the limits of what can be achieved. Be aware of how high frame rates impact your exposure (and light requirements). For any camera, regardless of sensor, regardless of manufacturer the same rules are true when it comes to high frame rates and exposure. It’s purely mathematics. Every time you double the frame rate, you are halving the exposure time for each frame… and halving the amount of light hitting the sensor. For an example, lets assume a “normal” shutter angle of 180 degrees. At 24 frames per second, with a 180 degree shutter gives us an exposure time of 1/48th sec. If we double the frame rate to 48fps, with the same shutter angle we halve the exposure time to 1/96th sec. We’ve just lost a full stop of light and are only at 48fps. Let’s extrapolate this out and I’ll rather use 25fps as a starting point instead of 24fps because it will multiply out with round numbers: 25fps @ 180deg = 1/50th sec 50fps @ 180deg = 1/100th sec (1 stop loss) 100fps @ 180deg = 1/200th sec (2 stop loss) 200fps @ 180deg = 1/400th sec (3 stop loss) 400fps @ 180deg = 1/800th sec (4 stop loss) Of course frame rates can be anywhere in between these numbers but I’ve simply doubled it every time for the example. So you can see we’re losing a stop of light every time we double the frame rate. Losing a full stop is not a small amount of light. Every stop lost is a halving of light. 1 stop loss = 1/2 the light 2 stop loss = 1/4 the light 3 stop loss = 1/8 the light 4 stop loss = 1/16 the light Just as a change in shutter angle at a normal frame rate affects exposure time and requires a compensation to be made in lens aperture or lighting, high frame rates require even more compensation beyond just opening up the lens. This means if you have enough light for a correct exposure at 25fps and you don’t want to affect your depth of field (by opening up your aperture), you’ll have to double the amount of light used to light your scene or subject to get the same correct exposure at 50fps. You’ll have to quadruple the amount of light on your subject to have a correct exposure at 100fps. This just doubles every time, so to have a correctly exposed image at 200fps you need 8x the amount of light on your scene as you would at a normal 25fps frame rate. The sun gives us plenty of light for this, so outside under daylight, compensating for the much shorter exposure times when shooting high frame rates is much less of an issue. However, inside under artificial lighting… you have to crank up the light seriously (double it) every time you double the frame rate. It’s normal that high speed table top shoots for instance require a ton of light. If you are on set when shooting a product shot involving a liquid pouring and they have a Phantom on set shooting at 1000fps, they will have serious light on that product. 6. Base Sensitivity When it comes to high frame rates, a higher “native” base ISO or exposure index (EI) is always beneficial. Keep this in mind when comparing cameras. Every sensor is different and every camera will perform differently capturing high frame rates. If a particular camera gives brighter images at high frame rates, it’s either because the sensor has a higher base ISO or it can be pushed above its base ISO with acceptable noise. Base sensitivity of a sensor is down to many things, simplest of which is the size of the photosites (but that is a huge simplification), and this is determined by how many of them are crammed onto the sensor. If you increase resolution (or number of photosites) and keep sensor size the same, the photosites get smaller and as a generalization, base sensitivity will decrease. The amount of space between photosites is also a factor, and the amount of space needed for circuitry at each photosite. 7. Shot Noise In the end regardless of all this there is “shot noise”, a minimum level of “noise” when counting or detecting small numbers of photons that is due to variations in quantum probability. If you throw one single photon at a surface with 50% reflectance, there is a 50% probability that it will be reflected or absorbed. So that surface could show up if the photon is reflected and detected at a photosite, or it could be black if the photon is absorbed rather than reflected. The more photons that are thrown at the surface, eventually probability dictates that 50% will be reflected and 50% will be absorbed. If you flip a single coin, it will land either heads, or tails but there can only be one possible outcome and the probability is equal it could land either way. If you flip 1000 coins, you should on average count 50% heads and 50% tails. I don’t want to over-play “shot noise”, it’s only a factor at extremely low light levels, but I just want to point out that even if an image sensor is otherwise perfect (which none are), it does define a impenetrable minimum noise floor that is simply down to quantum physics. Other types of noise also come into play such as Fixed Pattern Noise (FPN) which is caused by non-uniformities of the sensor in the manufacturing process. FPN is fixed and can be mapped out, however other types of temporal noise are more difficult to reduce. 8. Light A image sensor will always perform best when there is plenty of light, and when you have very short exposure times for each frame (as in pushing higher frame rates) the only solution is more light. As I have explained before in “8 Essential Steps to Perfect Exposure – The Knowledge Any Cameraman Should Have” exposing your sensor properly is the single most important key to achieving the image you envision seeing beautifully graded and finished after post production.Read more
We all love to joke that we’ll fix it in post, but it doesn’t have to be that way. It does require a coherent thread of understanding from set lighting and perfect exposure, all the way to color correction. In this article we will take a close look at each step to remind us how to create a perfect picture and have less to worry about afterwards. We will have to nerd it up a bit, but just think – you won’t have to fix it in post anymore. The science will help set your creativity free. Just because you mostly work with the creative side of your brain does not mean you can leave the science and math alone. One cannot exist without the other. It’s about taking control of each step, but before you can have any kind of control – you need to understand what’s going on. 1. Light What is light? Well, of course we know light in terms of luminance and color information and that’s where all this will end up in a color-grading suite. However, we need to start at the very beginning. We first need to capture an image with a camera. So I want to start with light in its fundamental form. Visible light is energy in the form of electromagnetic radiation. Electromagnetic radiation is a fundamental phenomenon of electromagnetism, behaving as waves and also as particles called photons. A photon is massless and has no electrical charge. However, it exhibits what is called a photoelectric effect. For example, a photon travelling from a light source and landing on an electric plate will eject an electron. An electron does have a charge, and is therefore measurable. This is exactly what an image sensor does. It is effectively a high-resolution photon counter. The sensor is a vast array of microscopic photosites, and each photosite can be thought of as a well with depth and surface area. The deeper the well and the larger the surface area, the more photons a single photosite can capture. Lets imagine a 4K Bayer image sensor has 4096 x 2160 resolution, that means it has 8,847,360 active photosites. It actually has more, but let’s simplify. 2. The Inverse Square Law At this point I want to introduce a critical concept to know and understand as it affects everything downstream from set lighting and exposure all the way into post-production – the Inverse Square Law. The image sensor is effectively measuring light intensity. All of the light in a given scene has a source and light intensity follows the inverse square law. This means light intensity is inversely proportional to the square of the distance from the source of light. Light intensity does not fall off in a linear fashion. An object at twice the distance from a light source will receive only a quarter the intensity of light. 3. The Stop The word stop has a number of meanings and can be confusing. An aperture stop is a measure of input pupil or iris size in a lens limiting the amount of light passing through the lens and exposing the sensor. This is a ratio of lens focal length to iris diameter. For example, if a lens has a focal length of 50 mm and its iris diameter is 25 mm, the f-number is 2 and the aperture diameter is f/2. Lenses use a standard f-stop scale, which is a sequence of numbers corresponding to the sequence of the powers of the square root of 2: f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22 etc. These result in a logarithmic scale of light intensity. A stop is also used to quantify ratios of light, with every incremental stop meaning an increase by a factor of two, and every subtracted stop meaning a decrease by a factor of one-half. A stop is also known as one unit in exposure value or EV. In the sense of ratios of light intensity or exposure an increase or decrease by a stop has the same effect whether it is the iris of a lens or measurements of light intensity with a light meter. 4. Dynamic Range If you understand everything so far then you’ll be able to grasp the concept of dynamic range. Every camera manufacturer quotes the dynamic range of its sensor. This is because it’s a hugely important indicator of imaging performance. Dynamic range is simply the maximum possible range of exposure (in stops or EV) that an image sensor is capable of capturing. Remember that a one stop increase represents a doubling of light intensity. So a sensor capable of capturing a 12 stop dynamic range means that it will resolve pure white in highlights that are 4096 times as bright or intense as the light intensity at its black level. That is a maximum contrast ratio of 4096:1. A 13 stop dynamic range doubles this to 8192:1, and 14 stop range doubles it again to capture pure white at light levels 16,384 times as intense as it’s black point. 7 stops DR – 128:1 8 stops DR – 256:1 9 stops DR – 512:1 10 stops DR – 1024:1 11 stops DR – 2048:1 12 stops DR – 4096:1 13 stops DR – 8192:1 14 stops DR – 16,384:1 Anything less than the minimum light level will always be recorded as black (and as we know there’s also a certain amount of noise down there too) and any light that is more intense than the maximum level the sensor is capable of reading will just become pure white in terms of recorded image data. No image detail can be recorded beyond this maximum level even if it does exist in the scene. 5. Log Gamma Human vision perceives more detail and contrast with differences of luminance at the low and mid end of the scale than in extreme highlights. Our perception of brightness is not linear. There is also a limitation in the scale of data values that can be assigned to luminance in terms of the bit depth of our files. We want to make sure we record more useable luminance information toward the low and mid tones without sacrificing highlight detail. An image sensor has a linear response to changes in brightness. Therefore a function must exist between input luminance and the values we record. This function is a curve. A gamma curve is simply a function between linear changes in input luminance from the camera sensor, and corresponding levels of output luminance that are actually recorded. A roughly logarithmic gamma curve allows us to record increased or expanded luminance information in lows and mids where they are important, and less information in the highlights where we don’t perceive so much difference. Below are some example frames comparing log cameras files before and after correction. Below are some shots from the Blackmagic URSA in Film mode, RAW CinemaDNG. Some Arri Alexa shots, these were captured in Prores. Finally some Red R3D. An uncorrected image captured with a log gamma curve looks flat and washed out. Each camera has a slightly different look, naturally as each sensor is different. It won’t look natural before color correction, but your colorist will be able to work magic with all the extra information contained in the lows and mid tones. 6. Exposure Each frame of video we capture and record is a still image created by counting how many photons hit each photosite on the sensor in a fixed period of time. This is our exposure, and as far as the sensor is concerned it’s measured in eV or electron volts as an electrical charge at each photosite. eV (electron volts) is not to be confused with EV (exposure value). Image sensors respond to light linearly, so as light intensity increases, eV (electron volt) charge at the photosite increases linearly. EV (exposure value) however is logarithmic representing a doubling of light intensity for every increase in EV unit. Exposure time of course is determined by frame rate and shutter angle (or shutter speed). For example, if our frame rate is set to 24 frames per second, we have a maximum of 1/24th sec exposure possible for each frame. Furthermore, lets take a typical shutter angle of 180 degrees; this is exactly half of a full 360 degrees, meaning our exposure time is actually half of 1/24th sec, or 1/48th sec. Now, something incredibly important here needs to be said about ISO. An imaging sensor has what is known as a “native” or “base” ISO. This is its natural un-amplified level of sensitivity. It’s actually its only level of sensitivity. When you increase ISO setting in camera, all you are doing is under-exposing the sensor and amplifying its output signal. This increases noise substantially. A correct exposure is of course somewhat subjective and dependent on what you are shooting. Generally it can be considered that the brightest highlights of your scene do not over-saturate the photosites on the image sensor (unless the sun, or other bright light source is in frame), and the darkest areas of your scene (the lowest light level that you still want perceivable detail) is sufficiently above the noise floor of the sensor. But those are the limits at the extreme. Normally the range is somewhere in between. For instance if you are shooting outside on an overcast day, the total range may be far less than the maximum dynamic range of your sensor. So what about the middle? This is where having a middle grey card and white card on set with you becomes very useful. If you can pin down a middle grey and a white card correctly, the rest of your exposure should be in a good place. Every camera’s log color space has a slightly different gamma curve so I am going to give the average values here. A middle grey card has 18% reflectance, and on a waveform monitor should sit at about 40% IRE. If you don’t have a waveform monitor you can use the zebras. Just set zebras to 40% and your grey card will be at 40% when it starts to show the zebras. A white card has 90% reflectance and should be at about 60% IRE. A waveform or light meter are the best ways to set these values but zebra can be used if that’s all you’ve got at your disposal. In the shot above, I was clearly struggling with exposure. This was shot at night in the shell of an abandoned stone house in the woods (very cool location). The only light I had was from a fire in a fireplace nearby and an oil lamp which was meant to just be a practical light. Skin tones want to be exposed similarly to a middle grey card, and you can see from the histogram in Resolve it was way under. If I had just gone ahead thinking it could be pushed sufficiently in the grade I’d be dealing with all kinds of nasty noise resulting in unusable shots. The lens aperture was already opened up pretty much all the way and I didn’t want to push up ISO. So there was only one thing for it, and that was to increase ambient light to a level where my skin tones were pushed to between 40-50% IRE. Looking at the histogram these levels are much better. Because the total luminance range in this shot is quite limited, there actually isn’t much that is brighter than the skin tones. If you don’t like noisy images it’s always better to give your sensor more light so I recommend slightly overexposing. If you are working with any high dynamic range sensor you’ll have more or less 6 stops above middle grey, so you can bring down exposure in post to bring back highlights and you’ll have less noise in the blacks too. This is sometimes referred to as ETTR (Expose to the Right) and looking at a histogram you are shifting everything slightly toward to right side. Just how slight depends on your sensor so it’s important to know how many stops you have above and below middle grey at your sensor’s base ISO. You don’t have any control over the maximum limit of dynamic range for your camera sensor, but ideally you have control over the overall level of light illuminating your scene, and you can then also control the ratio of light between shadows and highlights. This is contrast. If you really want to take your lighting and cinematography to the next level, I would highly recommend you look at adding a light meter to your toolset and learning to use it. Controlled lighting is the key that unlocks the most beautiful cinematography. This is something, I fear, that is being lost and forgotten with the widespread trend of shooting under only existing light, which is all too often too little to get the best possible performance from our sensors. The desire and demand for ultra high ISO is killing the power and magic of purposeful and creative lighting. 7. Lighting Ratio Lighting ratio is most often considered the ratio between key light (creating your highlights) and fill light (filling in the shadows). This ratio is important when lighting subjects within your scene, however there is also an overall ratio in your scene that exists between extremes of shadow and highlight. What is important is an understanding of the concept that a ratio exists between shadow and highlight, and that this ratio (which can be calculated manually from incident light meter readings) ideally should not exceed the maximum contrast ratio dictated by the dynamic range of your camera sensor. As for lighting subjects within your scene, the style you are aiming to achieve plays an important role. This is where low-key and high-key lighting comes in; this is contrast within your image. Do you want extreme contrast between objects that are lit and shadows or should it be more naturally balanced? Often the ratio of fill to key on a subject can be controlled with a simple reflector as is the case pictured here from one of my short films. It’s also important to take into consideration what you plan to do with the captured image in post. A colorist can only work with the image they are given, and that is all decided by what happens on location or on set. 8. Lift Gamma Gain Finally we come to the end, as I promised where all of this ends with digital files full of luminance and color information. What you will have captured if you’ve lit with your lighting ratios and sensor dynamic range in mind, and exposed properly is all the right information from your scene at the right levels in your image files. This means zero to fix in post. You will be able to easily balance, color correct and make tweaks to your image if your shadow details, mid tones and highlights all sit where they should be. But where exactly should they be in your final color corrected image? This is where balancing the luminance levels comes in, and it’s one of the first steps in color correction. One reference that I always use is the tried and true 10 zone Ansel Adams exposure system that has existed in the world of print photography for a long time. It’s not rocket science to use either. Based on the sensitometry research of Ferdinand Hurter and Vero Charles Driffield, the system provides a reference for achieving a correctly visualized film print from a correctly exposed film negative. The system has been applied to all forms of photography including digital. The system divides exposure into 10 zones from black to white and is used as a reference for what image elements at their respective levels of luminance should fall into each of these zones. The below frame grab (from Into The Wild) has been marked up to illustrate the zones. Color information is not needed so we’re looking at luminance only. 0 – Pure black 1 – Near black, slight tonality, no detail 2 – Dark black, slight detail in shadows 3 – Very dark grey, distinct shadow texture is visible 4 – Medium dark grey, slightly darker black skin, dark foliage, landscape shadows 5 – Middle grey, 18% grey, darker tan white skin, lighter black skin, light foliage, dark blue sky 6 – Middle light grey, average white skin, light stone, shadow areas on snow 7 – Light grey, pale white skin, concrete or grey asphalt in sunlight 8 – Grey white, pale detail in highlights, white wall in sunlight, bright surfaces 9 – Bright white, slight detail in highlights, white paper, snow, white water 10 – Pure white, no detail, light sources, specular highlights Bottom line. Color correction and grading is the last part of the thread that I hope I have tied through all of this. Your goal is a beautiful, rich, styled and clean color graded picture. In order to achieve this, the required image information must be in your files, and therefore must have been captured with a properly exposed camera sensor and a properly lit scene. Light is your best friend. When it comes to crafting beautiful images less is not more.Read more
Coming from a DSLR background, many shooters have a similar procedure for exposing their image: Shutter 1/50th, ISO low as possible, ND and aperture to suit. However implementing this method on other cameras can be detrimental to your image. The Canon C100/C300 has a base ISO of 850, use this for best results. It may be a simple and obvious procedure for some, but having met quite a few shooters over last few months that weren’t aware of this, I felt it worth writing a quick article on. The native ISO on both the Canon C100 and C300 cameras is 850; anything below or above this is compensation. Unlike shooting raw, raising the ISO in-camera is still a critical point of exposing the 8-bit internal codec of the Canon cameras, however it is the reduction of ISO speeds that I want to talk about. It is best to present this in the form of screen shots, here below is an image taken from my C100 (out of my window quickly so nothing award winning or scientific), as you can see by the overlays I am using an ISO of 850 and an aperture of f/5.0 with 6 stops of ND. My shutter is 1/50th and my picture profile Cinema EX (I choose not to display these overlays to keep the screen display clean). It’s a dramatic shot in terms of dynamic range, but you can see cloud detail, and highlight peaks are limited. I’ve added a waveform overlay from Premiere Pro on the right hand side so you can see what’s happening with the information. Here’s the same shot, but using a lower ISO of 320; this is typically how you would approach exposure with a 5D mark iii for example. I’ve compensated for exposure by reducing the ND to 4 stops, and opening the aperture to f/4.0. In terms of exposure these settings should be fine, but look at the waveform, it’s flat lining before the top of the graph. So what’s different? With the latter setup, you are letting more light hit the sensor by reducing physical attributes which affect exposure – ND and aperture. As the ISO level of 320 is over a stop lower than the base level of the sensor (which is 850), the sensor can’t handle it and is losing information in the highlights, despite on paper the settings being within the range of correct exposure. Just look at the cloud detail for proof, all information is gone and what’s left is a grey mess. By shooting with the native ISO of 850, you are using the base level of sensor, any exposure adjustments are physical ones (aperture and ND) which stop/allow light from hitting the sensor. Canon has kindly set a reminder in the overlays by adding brackets around ISO 850 so you don’t forget. Stick to ISO 850 as much as you can; I never dip below it. In lowlight situations I’ll raise to dependant on situation, this does not have the same detrimental effects; you can raise the ISO above 850 should you require (just be aware that the higher your ISO rises, so does the amount of noise present within the image). This is not a procedure restrained to the Canon C100 and C300 cameras, the Sony F55 works on a base ISO of 1250, and the A7S 3200. The difference in these cameras are that when operating in S-Log modes, you physically can’t reduce the ISO levels below its native setting; quite a handy feature when you consider what your image can end up like if you were to simply exposure without consideration for the base ISO of your camera.Read more
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